uTrack24 channel slew

I recently bought a uTrack24 to evaluate as a recorder for a 24-channel hydrophone array we are using for underwater noise measurements. Not, I admit, the standard application, but on paper the uTrack24 seems ideally suited to the purpose. I’ve been doing a bunch of tests on it and all except one indicate it will work extremely well. The one issue is that the signals recorded on channels 7, 8, 15, 16, 23 and 24 appear to be delayed with respect to the other channels by 119 microseconds (at 48 kS/s) or 129 microseconds (at 44.1 kS/s), both of which correspond to a delay of 5.7 samples. All other channels align precisely, and the six ‘slewed’ channels align precisely with one another. (The tests were done using the Utrack 24’s internal clock.) We will be doing beamforming with the array which requires precise timing between the channels so I’m wondering why this channel slew is occurring. If we can rely on it always being the same then we can compensate for it in our post-processing software. The worst case scenario would be if it isn’t consistent between recordings. Any light you can shed on this would therefore be appreciated. Alec